Pump driven by inverter
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I have a magnetic pump with a flow rate of 20 m3/h, a head of 50 m, a rotation speed of 2960 rpm, and an outlet pressure of 0.4 MPa. I need to modify this pump by installing a frequency converter in order to reduce the flow rate to 1.5 m3/h, while keeping the outlet pressure as stable as possible. Is this feasible? Given that the rotational speed is proportional to the square of the head and flow rate, will the outlet pressure become extremely low when the flow rate increases to 1.5 m3/h, making it impossible to meet the requirements?
This post was last edited by ccxpl on 2020-4-6 at 11:57. The flow rate has decreased from 20 cubic meters to 1.5 cubic meters; the outlet pressure is 0.4 MPa, and the length remains at 40 meters. It’s necessary to consult the pump’s performance curve. The flow rate is too low; it’s as if all the valves are closed. The pump will vibrate heavily, and that’s not acceptable. It has nothing to do with whether the frequency is variable or not. When the speed decreases, both the head and flow rate drop as well.
Install a circulation pipe for reflux before entering the device, and add a switch valve and a control valve to regulate the flow rate.
The cost is high; it’s better to buy a new pump.
With variable frequency control, adjusting the speed means that to reduce the flow rate, the speed must be lowered; however, this also results in a decrease in head pressure. It is not possible to reduce only the flow rate without affecting the head pressure. Either a different pump needs to be used, or an automatic valve must be employed for adjustment
The design institute is telling you, what a joke – flow rate and rotational speed are directly proportional to each other. If your flow rate is reduced by 10 times, the corresponding rotation speed should also be reduced by 10 times. And the rotational speed is in a square relationship with the head; go ahead and calculate it. Your motor can’t take it either. At such a low frequency, it would have burned out long ago.
1.5 m3/h – this flow rate requirement is already below the pump’s MCSF. If the flow rate required by the process is higher than the pump’s MCSF, then it is possible to meet that requirement. You can search on Baidu for ITT’s Pump-Smart system; however, installing such a control system on this small pump would likely make it more expensive than the pump itself, which isn’t practical. It is recommended to either replace the pump or use a recirculation system.
With that energy, can’t you just buy a new pump?